Insulated underground conduit



April 1967 J- P. KELLER INSULATED UNDERGROUND CONDUIT 2 Sheets-Sheet 1 Filed May 10 1963 April 11, 1967 P, KELLER 3,313,321

I NSULATED UNDERGROUND OONDUI T Filed May 10, 1963 2 Sheets-Sheet 2 INVENTOR 17267 265 Efliieg BY I {4% w j zw ATTORNEYS United States Patent M 3,313,321 INSULATED UNDERGROUND CONDUIT James P. Keiler, Springfieid, Va., assignor to Rensulate Corporation, Silver Spring, Md, a corporation of Maryland Filed May 10, 1963, Ser. No. 279,492 3 Claims. (Cl. 138105) This invention relates to improvements in insulated underground conduits and to apparatus for and methods of producing same.

In the art of insulating underground pipes or other conduits for hot or cold fluids it has been heretofore wellknown to support the pipe in a trench in spaced relation from the bottom and sidewalls of the trench, and to pour insulating concrete or other conventional insulating masses in the trench and around the pipe. customarily such insulating concretes have been comprised of an insulating aggregate such as expanded vermiculite together with a binder which generally consists of water settable cement, as for instance Portland cement. It has generally been necessary to provide a parting coating or wraping around the pipe in order to prevent adherence to it of the insulating concrete such as would result in damage to the concrete due to the thermal expansion and contraction of the pipe, the concrete normally having a different rate of expansion and contraction and normally being of insufficient tensile strength to resist cracking when the pipe expands in the event it should adhere to the pipe. Due to the comparatively long time required for setting or curing of the concrete it has been necessary to embed supports within the molds and in the insulating concrete itself to support the pipe both during the period of setting of the concrete while adjoining sections are being poured and also for subsequent expansion and contraction within the concrete insulation material. The backfilling of the trenches has been necessarily delayed until after the concrete or insulating concrete has been properly cured. It is necessary to await drying out of mixing Water before the concrete reaches its maximum insulating efficiency.

All of this has extended both the time and the cost required for the application of insulating concrete to pipes and the like, and in addition in extremely cold climates it has been necessary either to cease operations when the weather is below freezing or to take diflicult and expensive measures to prevent freezing of the insulating concrete.

Further, due to the inability of such prior insulating material to flex without breaking or cracking, it has been necessary to space same away from the pipe at expansion bends or loops in order to allow room for the pipe itself to flex without breaking the insulation.

The present invention has been conceived with the foregoing in mind and it is accordingly 2. primary object of the invention to provide an underground insulated pipe structure in which the pipe is embedded or encompassed within a monolithic sheath of stiffly resilient plastic foam material having suflicient elasticity that it may be poured around the pipe in direct intimate contact therewith and may even adhere thereto, but will nevertheless be capable of thermal expansion and contraction with the pipe without damage, While affording a greatly improved insulating ability as well as an increased degree of impermeability to water or moisture as contrasted to prior know insulating materials.

It has been found that a suitable foamed-in-place self expanding and self curing plastic foam material such as a polyurethane foam, after being poured and expanded around the pipe, cures itself within a matter of minutes to permit immediate maximum efficiency and rapid removal and reuse of the mold forms or boards for the pouring of a further section of sheathing around the pipe and to permit immediate backfilling of the trench over the section just poured.

3,313,321 Patented Apr. ll, 1967 The material immediately after setting also incorporates suflicient strength to provide the sole support for the pipe enclosed within it without the necessity for any rigid inserts or suspension means for this purpose. Moreover, the resilient flexibility of the material is such as to permit its being poured directly around and in intimate contact with the expansion ends or loops of the pipe and to flex with these without damage and without having to be spaced from these flexing sections of the pipe as heretofore in order to avoid interference with their movement.

The invention further contemplates the provision of a novel and economical method of insulating the underground pipes by the pouring of a flowable self expanding and curing plastic foam into a trench around the pipe, allowing it to expand and to encompass and directly contact the pipe and then to cure itself.

In this application and as exemplified in the accompanying drawings I have disclosed only the preferred mode of carrying out the invention, though it will be readily appreciated that the invention is capable of other and different embodiments both as to the structure and the method without departing from the spirit and scope of the invention.

In the accompanying drawings:

FIGURE 1 represents a plan view of an open trench containing a plurality of pipes about which a section of insulation has been molded in accordance with the invention, the mold still being in place.

FIGURE 2 is a vertical cross section on the line 2-2 of FIGURE 1.

FIGURE 3 is a vertical section through the completed insulated pipe structure of the invention after curing of the insultation and removal of the mold.

FIGURE 4 is a section on the line 44 of FIGURE 1 illustrating the manner in which the side panels of the mold assembly are removably positioned in the bottom of the trench, and

FIGURE 5 is a vertical section showing the manner in which the insulating material in accordance with the invention encompasses and intimately contacts an expansion bend or joint in the pipe for flexing therewith incident to thermal expansion and contraction of the pipe.

Referring now in detail to the accompanying drawings and referring first to FIGURES 1 and 2 there is illustrated in these a plurality of metal pipes 10, 11, 12 and 13, extending adjacent the bottom of a trench but in spaced relation to both the sides and bottom of the trench. It will be understood that the pipes will be supported above the bottom of the trench by jacks, blocks or other suitable means which will neither be enclosed within the forms nor incorporated in the completed insulating structure, but rather will be located in advance of the mold. In other words, the pipes will normally be unsupported within the form itself.

These pipes 10 to 13, inclusive, will normally be of metal such as rigid iron or steel and frequently will extend for hundreds of feet so that they will normally expand or contract to a very considerable extent responsive to changes in their temperature. Accordingly, as shown in FIGURE 5 of the drawings, it will be customary to pr0 vide some suitable expansion means such as the expansion bend or loop therein shown. As is customary in the art, normally this expansion bend will include at least one section 10A extending transversely to the adjoining portions 108 and 10C, respectively, of the pipe for angular displacement responsive to thermal expansion and contraction of the pipe.

In order to dispose the foam around the pipes as shown in FIGURES 1 and 2, it has been found desirable to provide around the pipes a composite mold structure comprised for the most part of readily removable and rep1aceable sections arranged so that immediately after the pouring and curing of a given section or length of insulating material the mold may be removed and replaced along an immediately adjoining length of pipe.

Thus the form, generally designated 15, is preferably adapted to be placed at successive positions along the length of the pipes so that sections of the insulation may be successively molded along the entire lengths of the pipes through 13.

The mold itself is preferably comprised of a pair of normally vertical parallel side boards or panels 17 and 13, respectively, of any rigid material such as wood, composition board, plywood or metal. These are normally placed on edge in the bottom of the trench at the desired space apart and each is removably maintained in this position by a pair or more of stakes such as 19 of FIGURE 4, having their pointed lower ends 20 driven into the ground and having slidable collars 21 thereon, each supporting a holding finger 21A which depends inside of the form for holding the panels against the stakes. Stops 21B and 210 on the stakes limit the sliding movement of the collars.

In order to prevent direct contact of the molded insulating material with the bottom of the trench, as well as to provide a glazed moisture impervious smooth surface or skin on the molded sheath of insulating material, it has been found desirable to line the interior of the mold thus formed with a smooth sheet of flexible plastic material 22 such as polyethylene. This material will be arranged to extend throughout the entire length of the mold structure. It rests on the bottom of the trench to define the bottom of the mold, with its outer lateral edges extending up the inside wall defined by the side panels 17 and 18 and folded outwardly over the upper edges of these panels, as best shown in FIGURE 2.

For the purpose of confining the molded material within the mold so that during its expansion it will penetrate completely between the pipes 10 through 13 and into the various corners without leaving any undesirable voids, there is provided a cover or lid 25 which is supported preferably at any of various desired levels by means of the adjustable brackets 26 as shown. The mold cover 25 will normally afford a platform on which workmen will stand while injecting the plastic foam into the interior of the mold, and the weight of the workmen will tend to maintain the lid held down in place against the upward expanding pressure of the expanding material.

Each bracket 26 is of inverted U-shape, having its depending legs formed with relatively spaced horizontally registering pairs of perforations or openings 31 through any of which may be passed the pin 32 adapted to extend across the upper edge of the panel to adjustably position the bracket thereon. At its depending inner end, the innermost leg 28 is provided with a horizontally directed ledge 34, on which the mold lid or cover 25 is supported.

It is desirable further to interconnect the upper edges of the side panels 17 and 18 at intervals, preferably by adjustable tie rods such as shown in which each such tie rod includes relatively telescopically connected members 36 and 38 respectively formed with the depending downwardly turned hook portions 36, 38 respectively depending along the outside of the panels 17 and 18 to prevent their relative spreading. These are adjustably interconnected by means of the pin 40 adapted for selective positioning through any of the series of bores 42 through the tubular member 36 and a corresponding transverse bore (not shown) through the member 38.

Not only is the mold interior lined with polyethylene or other smooth surface plastic along its bottom and sides. In addition the under surface of the lid 10 also is provided with a lining consisting of a sheet 44 of polyethylene plastic adhesively or otherwise secured thereto.

For facilitating the injection of the foaming-in-place plastic material into the mold interior it is desirable to provide the lid 25 with a series of openings 46 disposed at suitable intervals along its length and of sufiicient diam eter to snugly receive the injection nozzle 48 leading from and communicating with a suitable supply of the material and/or its ingredients. The nozzle 48 may be inserted progressively in different openings 46 along the length of the mold to fill it from one end to the other. The holes 46 which are not in use permit the escape of air from the mold and also permit observation of the extent to which the mold is filled at any given time. Since the openings above those portions of the molds which have been filled with material will in many instances permit escape of the material during its expansion, the workmen will normally progressively plug these openings as they proceed with the filling operation in a direction lengthwise of the mold.

The mold normally needs no cover or obstructing means at its ends. Normally one of the longitudinal ends of the mold will be blocked by a section of insulation just poured and expanded or, in the case of the first poured section, will be blocked by a building wall through which the pipes emerge. The other or free end of the mold may be left open. While a certain amount of the expanding plastic foam will be extruded from this end, the viscosity of the material is normally such that the mold is nevertheless completely filled without the formation of any substantial voids or cavities and this extruded free end portion is subsequently incorporated in the next section of insulating material to be poured and molded.

Any of various foaming-in-place and self curing plastic foams or foam compositions may be employed in practicing the invention, so long as the resulting foam insulation product has the requisite insulating ability or characteristic, together with sufficient qualities of elasticity or stretchability and flexibility to enable it to expand and contract with the pipes and to deform with any expansion loops or bends enclosed therein without damage. The preferred type of foam for this purpose is a conventional polyurethane foam. Such a foam, or rather the ingredients therefor, are commercially available under the trade name Isofoam through Isocyanate Prod= ucts, Inc. of Wilmington, Del. This is a two-component rigid urethane foam produced by a two step chemical reaction. The first step involves the reaction of a pro pylene oxide adduct of sorbitol with toluene di-isocyanatet The second step is to react the product of the first reaction with a resin blend of additional sorbitol, catalyst and appropriate blowing agent such as Freon gas, which gas is well-known and may be one of a group of fluoro= chloromethane gases. The actual mixing of the ingredients or components for carrying out the said second step generally occurs in the nozzle 48 just prior to ejec-- tion of the mixed ingredients or components therefrom, the nozzle 48 being any suitable mixing nozzle. A suitable nozzle for the purpose is disclosed in the Barn Patent 2,739,843 of March 27, 1956.

The resulting reaction of the components, which oc= curs after they are extruded from the nozzle 48 and into the mold cavity, is exothermic in nature so that the Freon or other blowing agent is caused to vaporize and expand to produce the expanded foam product.

After the mold has been completely filled it is only a matter of minutes normally before the plastic material will have fully expanded and cured, following which the mold may be disassembled and moved to a new location for pouring another section, leaving only the polyethylene sheet 22 in position.

The use of polyethylene as a linings 22 and 44 for the mold has an important and multiple advantage, since due to its extremely fine structure and exceedingly smooth imporous surface, it constitutes one of the few substances to which the molded material will not adhere. Therefore, it functions as an effective parting material 44 to facilitate the ready removal of the mold cover or lid 25. In addition, however, this extremely smooth surface of the polyethylene sheet 44 on the lid and of the sheet 22 on the sides and bottom of the mold results in the formatlon over the entire outer surface of the molded insula tion block or body of a glazed skin or surface which is extremely impervious to penetration by moisture either in the form of liquid or vapor which might, if permitted to enter the material, partially destroy its insulating qualities.

After the removable portions of the mold have been removed it has been found desirable to fold the lateral edges or" the polyethylene sheet 22 inwardly in overlapping relation across the top of the completed structure and to seal these overlapping portions together by a suitable cement or waterproof mastic designated by the numeral 49 in FIGURE 3.

Thus the completed structure as shown in cross section in FIGURE 3 Will comprise, in addition to the pipes, a completely monolithic sheath or body 55 of expanded and cured plastic foam which completely encompasses the several pipes 10, 11, 12 and 13 in direct and intimate contact with each said pipe, the cured foam being sufficiently resilient to expand and contract with the pipes. The unicellular structure of such a foam renders it resistant to moisture penetration even though its skin is breached. However, its resistance to penetration even of moisture vapor is greatly increased both by its smooth glazed sldn as well as by the sheet of polyethylene 22 which immediately overlies the same.

While the foam is of suflicient resiliency or flexibility as well as elasticity to permit expansion and contraction thereof with the pipes without cracking or otherwise damaging the insulating foam, the foam is nevertheless of sufiicient strength to constitute the sole support for the pipe and it is unnecessary to provide separate inserts either for permitting expansion and contraction of the pipe or for supporting it.

Moreover, as is clearly shown in FIGURE 5, the pipe may be provided at suitable intervals with suitable expansion joints or bends such as shown including at least one relatively transversely extending section disposed between and connected to the longitudinally extending pipe sections 19B and 19C, respectively, on either side thereof whereby the longitudinal expansion and contraction of the sections 1013 and 16C will result in relative angular displacement of the transverse section A to accommodate this expansion and contraction. By virtue of the stifily resilient nature of the material forming the insulating sheath 50 it will be readily apparent that it may also be provided with a transversely disposed portion 50A coextensive with the transverse pipe section 10A and in intimate direct contact therewith at all points as with the remaining sections of pipe. Notwithstanding this the flexibility of the insulating material will permit ready deformation of the section 50A together with the pipe bend or section 10A without in any way cracking. damaging or otherwise impairing the insulation or its function.

It will be readily apparent from the above that 1 have conceived of an insulated pipe structure in which the insulation may have far greater insulating qualities than heretofore and yet which does not require the application of any winding or parting between it and the pipe to which it is applied due to its ability to expand and contract with the pipe. Moreover, such materials is of an inert nature and not subject to chemical decomposition.

E It may be applied without regard to the outside temperatures since the exothermic reaction involved during its application provides sufficient heat for its proper curing, even at below freezing temperatures, as well as for the expansion of its blowing agent. The fact that it cures Within a matter of minutes permits prompt backfilling of the trench, as the application of the material progresses, as well as rapid formation of successive molded sections of material. It is thus made possible to form an insulated conduit structure in accordance with the invention at a rate which is a multiple of that normally achievable by conventional methods.

Having thus described my invention, I claim:

1. An underground insulated pipe structure in a trench therefor comprising at least one pipeline containing runs of straight piping and fittings and a monolithic sheath of weight-supporting stiffiy resilient unicellular plastic foam material sufiiciently resilient to withstand thermal expansions and contractions in said pipeline by virtue of concomitant contractions and expansions in the individual cell volumes or" said foam, said sheath encompassing said pipeline and in direct intimate contact with substantially the entire exterior surface of said pipeline, the outside contours of said sheath being in general conformance with those of said trench rather than those of said pipeline.

2. The underground insulated pipe structure of claim 1 wherein said foam material is polyurethane.

3. The underground insulated pipe structure of claim 1 wherein said pipeline has a section intermediate of its length disposed transversely to adjoining portions thereof for angular displacement responsive to thermal expansion and contraction of said pipe, said sheath encompassing said transversely disposed section and in direct intimate contact with the entire exterior surface thereof.

References Qited by the Examiner UNITED STATES PATENTS 857,586 6/1907 Boyle 25-32 857,587 6/1907 Boyle 25-32 1,871,508 8/1932 Gardner 138-149 2,532,587 12/1950 Williamson 138-149 2,782,251 2/1957 Ebel et al. 2,843,913 7/1958 Barron 61-722 2,857,931 10/1958 Lawton. 2,901,775 9/1959 Goff 138-105 X 2,959,508 11/1960 Graham et al. 2,972,968 2/1961 Stafford 61-722 3,032,070 5/1962 Isenberg 138-149 3,144,050 8/1964 Maloney 138-103 X 3,151,633 10/1964 Shuman 138-149 X 3,204,668 9/1965 Emerson, et al. 138-158 OTHER REFERENCES Rigid Urethane Foam, Du Pont; received Dec. 26, 1962.

LAVERNE D. GEIGER, Primary Examiner.

L. J. LENNY, SAMUEL ROTHBERG, T. L. MOOR- HEAD, Assistant Examiners. 

1. AN UNDERGROUND INSULATED PIPE STRUCTURE IN A TRENCH THEREFOR COMPRISING AT LEAST ONE PIPELINE CONTAINING RUNS OF STRAIGHT PIPING AND FITTINGS AND A MONOLITHIC SHEATH OF WEIGHT-SUPPORTING STIFFLY RESILIENT UNICELLULAR PLASTIC FOAM MATERIAL SUFFICIENTLY RESILIENT TO WITHSTAND THERMAL EXPANSIONS AND CONTRACTIONS IN SAID PIPELINE BY VIRTUE OF CONCOMITANT CONTRACTIONS AND EXPANSIONS IN THE INDIVIDUAL CELL VOLUMES OF SAID FOAM, SAID SHEATH ENCOMPASSING SAID PIPELINE AND IN DIRECT INTIMATE CONTACT WITH SUBSTANTIALLY THE ENTIRE EXTERIOR SURFACE OF SAID PIPELINE, THE OUTSIDE CONTOURS OF SAID SHEATH BEING IN GENERAL CONFORMANCE WITH THOSE OF SAID TRENCH RATHER THAN THOSE OF SAID PIPELINE. 